Monoclonal antibodies

Question 1

what are monoclonal antibodies

Answer 1

• Monoclonal antibody = antibody produced from a single group of genetically identical (clones) B cells / plasma cells
• Identical structure
• Bind to specific complimentary antigen
• Have a binding site / variable region with a specific tertiary structure / shape
  -Only one complementary antigen will fit

Question 2

Why are monoclonal antibodies useful in medicine?

Answer 2

• Only bind to antigens because…
• Antibodies have a specific tertiary structure that’s complementary to a specific antigen which can bind to
  the antibody

Question 3

Explain how Monoclonal antibodies are used in targeting
medication to specific cell types by attaching a therapeutic
drug to an antibody e.g. in the treatment of cancer cells

Answer 3

Example: cancer cell

1. Monoclonal antibodies made to be complementary to antigens specific to cancer cells →
   cancer cells are abnormal body cells with different antigens (tumour markers)
2. Anti-cancer drug attached to antibody
3. Antibody binds / attaches to cancer cells (forming antigen-antibody complex)
4. Delivers attached anti-cancer drug directly to specific cancer cells so drug accumulates →
   fewer side effects e.g. fewer normal body cells killed

Question 4

Explain how Monoclonal antibodies can be used in medical
diagnosis e.g. pregnancy tests.

Answer 4

• Pregnant women have the hormone hCG in their urine
• Urine test strip has 3 parts with 3 different antibodies - position 1: antibodies complementary to hCG
• Middle, position 2: antibodies complementary to hCG-antibody complex
• End, position 3: antibodies complementary to antibody without hCG attached
• If pregnant - hCG binds to antibodies in application area = hCG-antibody complex
• Travels up test strip, binds to antibodies at position 2 = blue line
• If not pregnant - No hCG in urine so hCG doesn’t bind to antibodies in application area so doesn’t bind to antibodies at position 2 = no blue line
• Bind to antibodies at position 3 → blue line = control

Question 5

Explain the use of antibodies in the ELISA test`

Answer 5

• Can determine if a patient has

a) Antibodies to a certain antigen

b) Antigen to a certain antibody

• Used to diagnose diseases or allergies (e.g. HIV / Lactose
  intolerance)

Question 6

Explain why the use of controls when performing the
ELISA test is necessary

Answer 6

• Controls enable a comparison with the test
• To show that:
• Only the enzyme and nothing else causes colour change
• Washing is effective and all unbound antibody is washed
  away

Question 7

Explain why the secondary and detection antibody
must be washed away in the ELISA test

Answer 7

• Enzyme attached to antibody reacts with substrate
  turning the solution a different colour; indicates a positive
  result
• Not washed out → enzymes will react with the substrate
• Therefore give a positive result even if no antigen present
  (false positive)